Power converter device

ABSTRACT

The present invention provides a variable-speed control system which is capable of estimating saturation voltages of respective switching elements in the inverter operation to execute the saturation voltage compensation and thus getting an inverter output voltage indicated by a command value.

TECHNICAL FIELD

[0001] The present invention relates to a power converter device such asan inverter device for driving a motor at a variable speed, anuninterruptible power supply unit, or the like.

BACKGROUND ART

[0002]FIG. 11 is a view showing a configuration of an inverter device asa power converter device according to the related art.

[0003] In FIG. 11, reference numeral 30 is an AC power supply, referencenumeral 31 is an inverter device, reference numeral 32 is a converterportion for converting the AC power into the DC power, and referencenumeral 33 is a capacitor for smoothing the DC voltage. Also, referencenumeral 34 is an inverter portion for inverting the DC power into the ACpower that has the variable frequency and the variable voltage, theinverter portion having output power elements, which has self turnoffelements (referred to as “switching elements” hereinafter) Tr1, Tr2,Tr3, Tr4, Tr5, Tr6 and free wheeling diodes D1, D2, D3, D4, D5, D6.Also, Vuo is a potential of a connection point u between the switchingelements Tr1 and Tr2, Vv0 is a potential of a connection point v betweenthe switching elements Tr3 and Tr4, and Vw0 is a potential of aconnection point w between the switching elements Tr5 and Tr6.

[0004] Also, reference numeral 35 is a control portion forON/OFF-controlling the switching elements of the inverter portion 34,and reference numeral 36 is a motor such as the induction motor that isdriven at a variable speed as a load.

[0005] Also, reference numeral 40 is a CPU as an arithmetic circuit forreceiving various commands such as an operation command, a speedcommand, etc. and various set values such as anaccelerating/decelerating time, a V/f pattern, etc. as input signals,calculating an output frequency and an output voltage, and outputtingswitching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 to turn the switchingelements ON/OFF. Also, reference numeral 41 is a memory as a storingmeans for storing various data such as the accelerating/deceleratingtimes, a relational expression between the output frequency/outputvoltage, etc.

[0006] Also, reference numeral 42 a to 42 f are driving portions foramplifying the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2, which areoutput from the control portion 35, up to base signals having amplitudesthat can drive the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6.

[0007] As this output voltage controlling system, there are the pulsewidth modulation (abbreviated to “PWM” hereinafter) and the pulseamplitude modulation (abbreviate to “PAM” hereinafter). With referenceto the example of the PWM system that the output voltage is controlledby changing time periods during which the switching elements Tr1, Tr2,Tr3, Tr4, Tr5, Tr6 of the inverter portion 34 are turned ON, explanationwill be described hereinafter.

[0008] The CPU 40 receives various commands (not shown) such as theoperation command, the speed command, etc. and various set values suchas the accelerating/decelerating time, the V/f pattern, etc. stored inthe memory 41 as the input signals, calculates the output frequency andthe output voltage, and outputs the switching signals Su1, Su2, Sv1,Sv2, Sw1, Sw2 to turn the switching elements ON/OFF.

[0009]FIG. 12 is a view showing various waveforms of the inverter devicein the PWM system according to the related art, wherein (a) is a viewshowing relationships between command voltage waveforms Vur, Vvr, Vwr ina U phase, a V phase, a W phase and a carrier wave Vtri, (b) is a viewshowing a command voltage waveform Vu at a connection point u betweenthe switching elements Tr1 Tr2, (c) is a view showing a command voltagewaveform Vv at a connection point v between the switching elements Tr3and Tr4, (d) is a view showing a command voltage waveform Vw at aconnection point w between the switching elements Tr5 and Tr6, and (e)is a view showing an inverter output voltage waveform Vuv=Vu−Vv.

[0010] The CPU 40 compares the command voltage waveforms Vur, Vvr, Vwrshown in (a) with the carrier wave Vtri, and then brings the switchingelements into their ON state if the command voltage waveforms are largerthan the carrier wave, and brings the switching elements into their OFFstate if the command voltage waveforms are smaller than the carrierwave, as shown in (b), (c), (d).

[0011] Next, an operation of the inverter device according to therelated art will be explained hereunder.

[0012] When the power supply is turned ON, the converter portion 32converts the AC power of the AC power supply 30 into the DC power andsmoothes this DC power by the capacitor 33.

[0013] Also, the control portion 35 receives various commands such asthe operation command, the speed command, etc. and various set valuessuch as the accelerating/decelerating time, the V/f pattern, etc. as theinput signals, calculates the output frequency and the output voltage,and outputs the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 to turnthe switching elements ON/OFF.

[0014] Also, the inverter portion 34 converts the DC power into the ACpower having the variable frequency and the variable voltage byON/OFF-controlling the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6based on the switching signals Su1, Su2, Sv1, Sv2, Sw1, Sw2 output fromthe control portion 35.

[0015] The AC power having the variable frequency and the variablevoltage is supplied to the motor 36, whereby this motor 36 can be drivenat a variable speed.

[0016]FIG. 13 is a view showing output voltages of the inverter deviceaccording to the related art, wherein (a) is a view showing the voltagewaveform Vu0 at the connection point u, (b) is a view showing thevoltage waveform Vv0 at the connection point v, (c) is a view showingthe voltage waveform Vw0 at the connection point w, and (d) is a viewshowing the voltage waveform of the output voltage Vuv0 (=Vu0−Vv0).

[0017] In FIG. 13, E is a command voltage, Vuo is a potential waveformof the connection point u between the switching elements Tr1 and Tr2,Vv0 is a potential waveform of the connection point v between theswitching elements Tr3 and Tr4, Vw0 is a potential waveform of theconnection point w between the switching elements Tr5 and Tr6, andVTr1_ON, VTr2_ON, VTr3_ON, VTr4_ON, VTr5_ON, VTr6_ON are saturationvoltages, respectively when the switching elements (Tr1, Tr2, Tr3, Tr4,Tr5, Tr6) are turned ON.

[0018] As shown in FIG. 13, in the ON/OFF control of the switchingelements (Tr1, Tr2, Tr3, Tr4, Tr5, Tr6), the saturation voltages(VTr1_ON, VTr2_ON, VTr3_ON, VTr4_ON, VTr5_ON, VTr6_ON) are present whenthe switching elements (Tr1, Tr2, Tr3, Tr4, Tr5, Tr6) are turned ON.Therefore, the potential Vu0 at the connection point u has an amplitudeof E-VTr1_ON˜VTr2_ON as shown in (a), the potential Vv0 at theconnection point v has an amplitude of E-VTr3_ON VTr4_ON as shown in(b), and the potential Vw0 at the connection point w has an amplitude ofE-VTr5_ON˜VTr6_ON as shown in (c).

[0019] For this reason, the output voltage Vuv0 when the switchingelements Tr1, Tr4 are turned ON is given as not Vuv0=E−0=E, but$\begin{matrix}{{Vuv0} = \left( {{Vu0} - {Vv0}} \right)} \\{= {\left( {E - {VTr1\_ ON}} \right) - {VTr4\_ ON}}} \\{= {E - {\left( {{VTr1\_ ON} + {VTr4\_ ON}} \right).}}}\end{matrix}$

[0020] In contrast, the output voltage Vuv0 (=Vu0−Vv0) when theswitching elements Tr2, Tr3 are turned ON is given as not Vuv0=0−E=−E,but $\begin{matrix}{{Vuv0} = \left( {{Vu0} - {Vv0}} \right)} \\{= {{VTr2\_ ON} - \left( {E - {VTr3\_ ON}} \right)}} \\{= {\left( {{VTr2\_ ON} + {VTr3\_ ON}} \right) - {E.}}}\end{matrix}$

[0021] In the inverter device according to the related art, the commandvoltage is supplied to the inverter as the input voltage as it is.Therefore, the amplitude of the output voltage does not have theamplitude of the command voltage E˜−E, but the amplitude of the actualoutput voltage is in the range of

E−(VTr1_ON+VTr4_ON)˜E+(VTr2_ON+VTr3_ON),

[0022] whereby the part of the saturation voltages becomes the error.

[0023] It is possible to get the smooth output, in which the low orderharmonics contained in the output voltage of the inverter is reduced bythe PWM system. However, the command voltage is supplied to the inverteras the input voltage as it is, and thus the saturation voltages of theswitching elements in the inverter operation are not taken intoconsideration. Therefore, in the inverter operation, the inverter outputvoltage for generating the saturation voltage of the switching elementsdoes not coincide with the voltage indicated by the command value, andthus there is the problem that the precise voltage cannot be output.

[0024] Also, there is the system that the actual output voltage ismeasured such that the inverter output voltage coincides with the valueindicated by the command, and then the voltage that is subjected to thesaturation voltage compensation is input into the inverter. But thissystem needs to add the circuit separately, and thus there are theproblems that a cost is increased and a size of the circuit isincreased.

[0025] In addition, the input voltage of the motor is low in thelow-speed operation range, and the influence of the saturation voltageof the switching elements is enhanced relatively. Thus, there is theproblem that the speed ripple in the low-speed operation range isincreased.

[0026] The present invention has been made to overcome above suchsubjects, and it is a first object of the present invention to provide avariable-speed control apparatus that is capable of estimatingsaturation voltages of switching elements in the inverter operation toexecute a saturation voltage compensation and thus getting an inverteroutput voltage indicated by a command value.

[0027] Also, it is a second object of the present invention to provide avariable-speed control apparatus that is capable of estimating easilythe saturation voltages of switching elements in the inverter operation.

DISCLOSURE OF THE INVENTION

[0028] A power converter device of the present invention has an inverterportion having a switching element and a free wheeling diode element,the inverter portion for converting a DC power into an AC power, acontrol portion for ON/OFF-controlling the switching elements of theinverter portion, and a current sensor for sensing current flowingthrough one of the switching element and the free wheeling diodeelement, in which the control portion has a current discriminatingcircuit for discriminating that sensed currents sensed by the currentsensors are either current flowing through the switching elements orcurrent flowing through the free wheeling diode elements, a saturationvoltage estimation table for showing relationships between temperatureof the switching element, current value of the switching element,temperature of the free wheeling element, and current value of the freewheeling element and saturation voltages of the switching elements; anda saturation voltage compensating unit for receiving the temperature ofthe switching element and the current discriminated by the currentdiscriminating circuit, estimating a saturation voltage of the switchingelement by using the saturation voltage estimation table, and formingsaturation voltage compensated voltage in which a command voltage to aninverter is compensated with the estimated saturation voltage, and inwhich the switching elements of the inverter portion areON/OFF-controlled based on the saturation voltage compensated voltage.Therefore, the reduction in the inverter output voltage due to thesaturation voltage of the switching element can be prevented and thusthe more precise voltage control can be achieved.

[0029] A power converter device of the invention has an inverter portionhaving a switching element and a free wheeling diode element, theinverter portion for converting a DC power into an AC power, a controlportion for ON/OFF-controlling the switching elements of the inverterportion, and a gate voltage detecting circuit insulating circuit fordetecting gate voltage of the switching element, in which the controlportion has a current discriminating circuit for discriminating thatsensed currents sensed by the current sensors are either current flowingthrough the switching elements or current flowing through the freewheeling diode elements, a saturation voltage estimation table forshowing relationships between temperature of the switching element,current value of the switching element, temperature of the free wheelingelement, and current value of the free wheeling element and saturationvoltages of the switching elements, and a saturation voltagecompensating unit for receiving the gate voltage of the switchingelement and the current discriminated by the current discriminatingcircuit, estimating a saturation voltage of the switching element byusing the saturation voltage estimation table, and forming saturationvoltage compensated voltage in which a command voltage to an inverter iscompensated with the estimated saturation voltage, and in which theswitching elements of the inverter portion are ON/OFF-controlled basedon the saturation voltage compensated voltage. Therefore, even if theload is heavy and the saturation voltage is changed depending on themagnitude of the gate-emitter voltage in the ON-state of the switchingelements, the saturation voltage can be compensated with good precisionand thus the more precise voltage control can be achieved.

[0030] In addition, temperature sensors are fitted to the switchingelement and the free wheeling diode element to sense temperature of theswitching element and temperature of the free wheeling diode element.Therefore, the temperatures of the switching elements and the freewheeling diode elements can be sensed precisely.

[0031] Also, temperature sensor is fitted in the vicinity of theswitching element and the free wheeling diode element, which constitutea pair, on a substrate on which the switching element and the freewheeling diode element are mounted. The control portion estimatestemperature of the switching element and temperature of the freewheeling diode element based on substrate temperature sensed by thetemperature sensor, stationary thermal resistance between the switchingelement and the substrate, stationary thermal resistances between thefree wheeling diode element and the substrate, heating value of theswitching element calculated based on the sensed current, and heatingvalue of the free wheeling diode element calculated based on the sensedcurrent. Therefore, the fitting of the temperature sensors can befacilitated.

[0032] In addition, a temperature sensor is fitted to one location on asubstrate on which the switching element and the free wheeling diodeelement are mounted. The control portion estimates temperature of theswitching element and temperature of the free wheeling diode elementbased on substrate temperature sensed by the temperature sensor,stationary thermal resistance between the switching element and thesubstrate, stationary thermal resistances between the free wheelingdiode element and the substrate, heating value of the switching elementcalculated based on the sensed current, and heating value of the freewheeling diode element calculated based on the sensed current.Therefore, the fitting of the temperature sensors can be made much moreeasy.

[0033] Further, temperature sensors are fitted to a location on a finfitted to a substrate on which the switching element and the freewheeling diode element are mounted, the location corresponding to theswitching element and the free wheeling diode element. The controlportion estimates temperature of the switching element and the freewheeling diode element based on substrate temperature sensed by thetemperature sensors, stationary thermal resistance between the switchingelement and the substrate, stationary thermal resistance between the finand the substrate, stationary thermal resistance between the freewheeling diode element and the substrate, the stationary thermalresistance between the fin-the substrate and heating values of theswitching element calculated based on the sensed currents, and heatingvalues of the free wheeling diode element. Therefore, the fitting of thetemperature sensors can be further facilitated.

[0034] Furthermore, temperature sensor are fitted to a location on a finfitted to a substrate on which the switching element and the freewheeling diode element are mounted, the location corresponding to a pairof the switching element and the free wheeling diode element. Thecontrol portion estimates temperature of the switching element andtemperature of the free wheeling diode element based on substratetemperature sensed by the temperature sensor, stationary thermalresistances between the switching element and the substrate, astationary thermal resistance between the fin and the substrate,stationary thermal resistances between the free wheeling diode elementand the substrate, the stationary thermal resistance between the fin andthe substrate, heating value of the switching element calculated basedon the sensed current, and heating value of the free wheeling diodeelement calculated based on the sensed current. Therefore, the fittingof the temperature sensors can be made easy further more.

[0035] Besides, temperature sensor is fitted to one location on a finthat is fitted to a substrate on which the switching element and thefree wheeling diode element are mounted. The control portion estimatestemperature of the switching element and temperature of the freewheeling diode element based on substrate temperature sensed by thetemperature, stationary thermal resistances between the switchingelement and the substrate, stationary thermal resistance between the finand the substrate, stationary thermal resistances between the freewheeling diode element and the substrate, stationary thermal resistancebetween the fin and the substrate, heating value of the switchingelement calculated based on the sensed current, and heating value of thefree wheeling diode element based on the sensed current.

BRIEF DESCRIPTION OF THE DRAWINGS

[0036]FIG. 1 is a view showing a configuration of an inverter device asa power converter device according to an embodiment 1 of the presentinvention;

[0037]FIG. 2 is a view showing a saturation voltage estimation table inthe inverter device according to the embodiment 1 of the presentinvention;

[0038]FIG. 3 is a view showing an outer appearance of an inverter maincircuit of the inverter device according to the embodiment 1 of thepresent invention;

[0039]FIG. 4 is a view showing a configuration of an inverter device asa power converter device according to an embodiment 2 of the presentinvention;

[0040]FIG. 5 is a view showing a saturation voltage estimation table inthe inverter device according to the embodiment 2 of the presentinvention;

[0041]FIG. 6 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 3 of the present invention;

[0042]FIG. 7 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 4 of the present invention;

[0043]FIG. 8 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 5 of the present invention;

[0044]FIG. 9 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 6 of the present invention;

[0045]FIG. 10 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 7 of the present invention;

[0046]FIG. 11 is a view showing a configuration of an inverter device asa power converter device according to the related art;

[0047]FIG. 12 is a view showing various waveforms of the inverter devicein the PWM system according to the related art; and

[0048]FIG. 13 is a view showing output voltages of the inverter deviceaccording to the related art.

BEST MODE FOR CARRYING OUT THE INVENTION

[0049] Embodiment 1

[0050]FIG. 1 is a view showing a configuration of an inverter device asa power converter device according to an embodiment 1 of the presentinvention. In FIG. 1, reference numerals 30, 32, 33, 36, 40, 41, 42 a to42 f, Tr1 to Tr6, D1 to D6 are similar to those in FIG. 11, and thustheir explanation will be omitted. Also, reference numeral la is aninverter device, reference numeral 2 a is an inverter portion, referencenumerals 3 a to 3 f are current sensors, and reference numerals Iu1,Iu2, Iv1, Iv2, Iw1, Iw2 are sensed currents.

[0051] Also, the reference numeral Iu1, Iu2, Iv1, Iv2, Iw1, Iw2 arecurrents that flow through the switching elements Tr1 to Tr6 or the freewheeling diode elements D1 to D6, and directions indicated by arrowsshown in FIG. 1 are assumed as the positive directions.

[0052] Also, reference numeral 5 a is a control portion forON/OFF-controlling the switching elements of the inverter portion 2 a.Also, reference numerals 6 a to 6 f are current discriminating circuitsfor discriminating that the sensed currents Iu1, Iu2, Iv1, Iv2, Iw1, Iw2sensed by the current sensors 3 a to 3 f are either currents flowingthrough the switching elements Tr1 to Tr6 or currents flowing throughthe free wheeling diodes D1 to D6.

[0053] The current discriminating circuits 6 a to 6 f discriminate thatthe sensed currents Iu1, Iu2, Iv1, Iv2, Iw1, Iw2 sensed by the currentsensors 3 a to 3 f are either the currents that are flowing through theswitching elements Tr1 to Tr6 or the currents that are flowing throughthe free wheeling diodes D1 to D6. For example, the currentdiscriminating circuit 6 a discriminates the sensed current Iu1 sensedby the current sensor 3 a as

I _(u1TR) =Iu1, I _(u1D)=0 in the case of Iu1≧0, and

I _(u1TR)=0, I _(u1D) =Iu1 in the case of Iu1<0.

[0054] Also, reference numeral 7 a is a saturation voltage estimationtable indicating relationships among the temperatures of the switchingelements, the current values of the switching elements, the temperaturesof the free wheeling diodes, the current-values of the free wheelingdiodes, and the saturation voltages of the switching elements in theinverter operation, and reference numeral 8 a is a saturation voltagecompensating unit. Also, reference numeral 9 is a command voltagecorrecting portion.

[0055]FIG. 2 is a view showing the saturation voltage estimation tablein the inverter device according to the embodiment 1 of the presentinvention, wherein the gate voltage (the gate-emitter voltage VGE) is15V. In FIG. 2, a1 to a7 denote temperature/saturation voltagecharacteristics of the switching elements every current when thecurrents are flown through the switching elements, and b1 to b7 denotetemperature/saturation voltage characteristics of the free wheelingdiode elements every current when the currents are flown through thefree wheeling diode elements.

[0056] Now, a1 is the temperature/saturation voltage characteristic inthe case that the current flowing through the switching elements Tr1 toTr6 (referred to as an “I_(TR)” hereinafter) is 1 A, a2 is thetemperature/saturation voltage characteristic in the case that I_(TR)=5A, a3 is the temperature/saturation voltage characteristic in the casethat I_(TR)=10 A, a4 is the temperature/saturation voltagecharacteristic in the case that I_(TR)=20 A, a5 is thetemperature/saturation voltage characteristic in the case that I_(TR)=30A, a6 is the temperature/saturation voltage characteristic in the casethat I_(TR)=40 A, and a7 is the temperature/saturation voltagecharacteristic in the case that I_(TR)=50 A.

[0057] Also, b1 is the temperature/saturation voltage characteristic inthe case that the current flowing through the free wheeling diodeelements D1 to D6 (referred to as an “D” hereinafter) is 1 A, b2 is thetemperature/saturation voltage characteristic in the case that I_(D)=5A, b3 is the temperature/saturation voltage characteristic in the casethat I_(D)=5 A, b4 is the temperature/saturation voltage characteristicin the case that I_(D)=5 A, b5 is the temperature/saturation voltagecharacteristic in the case that I_(D)=5 A, b6 is thetemperature/saturation voltage characteristic in the case that I_(D)=5A, and b7 is the temperature/saturation voltage characteristic in thecase that I_(D)=5 A.

[0058] If the sensed currents Iu1, Iu2, Iv1, Iv2, Iw1, Iw2 sensed by thecurrent sensors 3 a to 3 f are different from the current values I_(TR)or I_(D) set forth in the saturation voltage estimation table, thetemperature/saturation voltage characteristic is estimated based on thetemperature/saturation voltage characteristic of the current valueI_(TR) or the temperature/saturation voltage characteristic of thecurrent value I_(D), that is close to the value in the table.

[0059]FIG. 3 is a view showing an outer appearance of an inverter maincircuit of the inverter device according to the embodiment 1 of thepresent invention. In FIG. 3, reference numeral 10 is a cooling fin,reference numeral 11 is a main circuit substrate, reference numeral 12is a case, reference numeral 13 is a switching element to which a sensor(temperature sensor) is fitted, reference numeral 14 is a free wheelingdiode element to which the sensor (temperature sensor) is fitted, Tr1 toTr6 are the switching elements, and D1 to D6 are the free wheeling diodeelements. In FIG. 3, there is shown an example in which the sensor(temperature sensor) is fitted to the switching elements Tr1 to Tr6 andthe free wheeling diode elements D1 to D6.

[0060] A voltage control in the inverter device according to theembodiment 1 will be explained with reference to FIG. 1 to FIG. 3hereunder.

[0061] In the control portion 5 a of the inverter device according tothe embodiment 1, the current discriminating circuits 6 a to 6 fdiscriminate in the inverter operation that the sensed currents Iu1,Iu2, Iv1, Iv2, Iw1, Iw2 sensed by the current sensors 3 a to 3 f areeither the currents flowing through the switching elements Tr1 to Tr6 orthe currents flowing through the free wheeling diodes D1 to D6, and thenoutput the current values I_(TR) or I_(D) (I_(u1TR), I_(u1D), I_(u2TR),I_(u2D), I_(v1TR), I_(v1D), I_(u2TR), I_(v2D), I_(w1TR), I_(w1D),I_(w2TR), I_(w2D)) to the saturation voltage compensating unit 8 a.

[0062] The saturation voltage compensating unit 8 a receives thetemperature Tj of the switching elements or that of the free wheelingdiodes sensed by the temperature sensors fitted to the switchingelements 13 in the inverter operation and the current values (I_(TR) orI_(D)) output from the current discriminating circuits 6 a to 6 f, thenestimates the saturation voltages of the switching elements by using thesaturation voltage estimation table 7 a, and then outputs the saturationvoltage compensated voltage in which the command voltage to the inverteris compensated with the estimated saturation voltage.

[0063] Assuming that the temperatures of the switching elements Tr1, Tr4in the inverter operation are Tj_Tr1, Tj_Tr4, the current values of theswitching elements Tr1, Tr4 are Iu1, Iu2, and the estimated saturationvoltages of the switching elements Tr1, Tr4 are Von(Tj_Tr1, Iu1),Von(Tj_Tr4, Iu2) when the switching elements Tr1, Tr4 are turned ON,after performing the voltage compensation by adding these saturationvoltages to the command voltage to the inverter, the input voltage E′ tothe inverter can be expressed by Eq.(1).

E′=E+Von(Tj _(—) Tr1, Iu1)+Von(Tj _(—) Tr4, Iu2)   (1)

[0064] Also, as shown in FIG. 13, the potentials Vu0, Vv0 of the pointu, the point v at a time when the switching elements Tr1, Tr4 are turnedON are given by

Vu0=E′−Tr1_ON   (2)

Vv0=VTr4_ON   (3)

[0065] and the output voltage Vuv0(=Vu0−Vv0) can be expressed by Eq.(4). $\begin{matrix}\begin{matrix}{{Vuv0} = {\left( {E^{\prime} - {VTr1\_ ON}} \right) - {VTr4\_ ON}}} \\{= {E^{\prime} - \left( {{VTr1\_ ON} + {VTr4\_ ON}} \right)}}\end{matrix} & (4)\end{matrix}$

[0066] By substituting E′ in Eq. (1) into Eq. (4), the output voltageVuv0 is given by Eq. (5). $\begin{matrix}\begin{matrix}{{Vuv0} = {E + {{Von}\left( {{Tj\_ Tr1},{Iu1}} \right)} + {{Von}\left( {{Tj\_ Tr4},{Iu2}} \right)} -}} \\{{{VTr1\_ ON} - {VTr4\_ ON}}}\end{matrix} & (5)\end{matrix}$

[0067] Here, since Von(Tj_Tr1, Iu1)≈VTr1_ON and Von(Tj_Tr4,Iu2)≈VTr4_ON, Eq. (5) can be expressed by Eq. (6).

[0068] the motor 36

Vuv0(=Vu0−Vv0)≈E   (6)

[0069] Thus, the output voltage E as indicated by the command value canbe obtained.

[0070] In contrast, assuming that the estimated saturation voltages ofthe switching elements Tr2, Tr3 are Von(Tj_Tr2, Iu2), Von(Tj_Tr3, Iv1)when the switching elements Tr2, Tr3 are turned ON, after performing thevoltage compensation by adding these saturation voltages to the commandvoltages to the inverter, the input voltage E′ can be expressed by Eq.(7).

E′=E+Von(Tj _(—) Tr2, Iu2)+Von(Tj _(—) Tr3, Iv1)   (7)

[0071] Also, as shown in FIG. 13, the potentials Vu0, Vv0 of the pointu, the point v at a time when the switching elements Tr2, Tr3 are turnedON are given by

Vu0=VTr2_ON   (8)

Vv0=E′−VTr3_ON   (9)

[0072] and the output voltage Vuv0(=Vu0−Vv0) can be expressed by Eq.(10). $\begin{matrix}\begin{matrix}{{Vuv0} = {{VTr2\_ ON} - \left( {E^{\prime} - {VTr3\_ ON}} \right)}} \\{= {{- E^{\prime}} + \left( {{VTr2\_ ON} + {VTR3\_ ON}} \right)}}\end{matrix} & (10)\end{matrix}$

[0073] By substituting E′ in Eq. (7) into Eq. (10), the output voltageVuv0 is given by Eq. (11). $\begin{matrix}\begin{matrix}{{Vuv0} = {{- \left( {E + {{Von}\left( {{Tj\_ Tr2},{Iu2}} \right)} + {{Von}\left( {{Tj\_ Tr3},{Iv1}} \right)}} \right)} +}} \\{{{VTr2\_ ON} + {VTr3\_ ON}}}\end{matrix} & (11)\end{matrix}$

[0074] Since Von(Tj_Tr2, Iu2)≈VTr2_ON and Von(Tj_Tr3, Iv1)≈VTr3_ON, Eq.(11) can be expressed by Eq. (12).

[0075] the motor 36

Vuv0(=Vu0−Vv0)≈E   (12)

[0076] Thus, the output voltage −E as indicated by the command value canbe obtained.

[0077] A command voltage correcting portion 9 prepares a voltage, whichis subjected to the saturation voltage compensation by adding thesaturation voltage, which is estimated by the saturation voltagecompensating unit 8 a, to the command voltage to the inverter withutilizing the characteristic data of the switching elements, and thenoutputs the voltage to the CPU 40.

[0078] The CPU 40 receives various commands such as the operationcommand, the speed command, etc. and various set values such as theaccelerating/decelerating time, the V/f pattern, etc. stored in thememory 41 as the input signals, calculates the output frequency and theoutput voltage, and outputs the switching signals Su1, Su2, Sv1, Sv2,Sw1, Sw2 to turn the switching elements of the inverter portion 2 aON/OFF.

[0079] The inverter portion 2 a converts the DC power into the AC powerhaving the variable frequency and the variable voltage byON/OFF-controlling the switching elements Tr1, Tr2, Tr3, Tr4, Tr5, Tr6.

[0080] In the inverter device according to the embodiment 1, thesaturation voltage estimation table that gives relationships between thetemperatures of the switching elements, the current values of theswitching elements, the temperatures of the free wheeling diodes, andthe current values of the free wheeling diodes and the saturationvoltages of the switching elements in the inverter operation isprovided, and then the saturation voltages of the switching elements areestimated based on the temperatures of the switching elements, thecurrent values of the switching elements, the temperatures of the freewheeling diodes, and the current values of the free wheeling diodes,which are detected in the inverter operation with utilizing thissaturation voltage estimation table and then the estimated saturationvoltage is employed in the control of the input voltage and the outputvoltage of the inverter. Therefore, the reduction in the output voltageof the inverter due to the saturation voltage of the switching elementscan be prevented and thus the more precise voltage control can beachieved. In addition, since the influence of the saturation voltage canbe reduced even in the low-speed operation range, the speed ripple canbe reduced.

[0081] Embodiment 2

[0082]FIG. 4 is a view showing a configuration of an inverter device asa power converter device according to an embodiment 2 of the presentinvention. In FIG. 4, reference numerals 3 a to 3 f, 6 a to 6 f, 9, 13,14, 30, 32, 33, 36, 40, 41, 42 a to 42 f, Tr1 to Tr6, D1 to D6, Iu1,Iu2, Iv1, Iv2, Iw1, and Iw2 are similar to those in FIG. 1, and thustheir explanation will be omitted. Also, reference numeral 1 b is aninverter device, reference numeral 2 b is an inverter portion, referencenumeral 4 a to 4 f are gate voltage detecting circuit insulatingcircuits, and VGu1, Vgu2, VGv1, VGv2, VGw1, VGw2 are gate voltages.

[0083] Also, reference numeral 5 b is a control portion forON/OFF-controlling the switching elements in the inverter portion 2 b.Also, reference numeral 7 b is a saturation voltage estimation table forshowing relationships between the temperature of the switching elements,the gate voltages of the switching elements, the temperatures of thefree wheeling diode elements, and the current values of the switchingelements, the free wheeling diode elements, and the gate voltages of thefree wheeling diode elements and the saturation voltages of theswitching elements in the inverter operation, and reference numeral 8 bis a saturation voltage compensating unit.

[0084]FIG. 5 is a view showing the saturation voltage estimation tablein the inverter device according to the embodiment 2 of the presentinvention, and there is shown the case where the emitter is grounded andthe substrate temperature Tc=125° C.

[0085] In FIG. 5, the collector-emitter voltage VCE in an ordinate thatextends over a range of 12 V to 18 V of the gate-emitter voltage VGE inan abscissa is the saturation voltage as the ON-state voltage of theswitching element. Also, c1 is a gate voltage/saturation voltagecharacteristic in the case that I_(TR)=100 A, c2 is a gatevoltage/saturation voltage characteristic in the case that I_(TR)=50 A,and c3 is a gate voltage/saturation voltage characteristic in the casethat I_(TR)=25 A.

[0086] In the case that I_(TR)=25 A, the saturation voltage is almostconstant as 2.2 V. However, in the case that the load is heavy likeI_(TR)=100 A, the variation becomes large as 4.4 V to 5 V and thereforethe saturation voltage is estimated to take the gate-emitter voltage VGEinto consideration, in the embodiment 2.

[0087] The saturation voltage estimation table 7 b in the embodiment 2is a (temperature-responsible) saturation voltage estimation table thatindicates relationships among the gate voltages and the current valuesof the switching elements and the saturation voltages of the switchingelements in the inverter operation, as shown in FIG. 5. The saturationvoltage compensating unit 8 b receives the temperatures Tj of theswitching elements and the free wheeling diode elements sensed by thetemperature sensors fitted to the switching elements 13 and the freewheeling diode elements 14 in the inverter operation, the current values(I_(TR) or I_(D)) output from the current discriminating circuits 6 a to6 f, and the gate voltages VGu1, Vgu2, VGv1, VGv2, VGw1, VGw2 sensed bythe gate voltage detecting circuit insulating circuits 4 a to 4 f, thenestimates the saturation voltages of the switching elements by using thesaturation voltage estimation table 7 b, and then generates thesaturation voltage compensated voltage in which the command voltage tothe inverter is compensated with the estimated saturation voltage.

[0088] In the above, there is explained the example wherein thetemperature sensors are fitted to the switching elements and freewheeling diode elements, respectively in the inverter main circuit inwhich the switching elements and the free wheeling diode elements arecomposed of separate elements from each other. However, in the case ofthe integrated element in which the switching elements and the freewheeling diode elements are incorporated into one element, thetemperature sensor is fitted every integrated element.

[0089] In the embodiment 2, the saturation voltage is estimated withtaking the gate-emitter voltage into consideration. Therefore, even ifthe load is heavy and thus the saturation voltage is changed dependingon the magnitude of the gate-emitter voltage in the ON-state of theswitching elements, the saturation voltage can be compensated with goodprecision and the more precise voltage control can be achieved.

[0090] Embodiment 3

[0091]FIG. 6 is a view illustrating the temperature measurement of theswitching element and the free wheeling diode element in an inverterdevice according to an embodiment 3 of the present invention, wherein(a) is a view showing an outer appearance of an inverter main circuit inwhich the temperature sensors are fitted in the vicinity of theswitching elements and the free wheeling diode elements constituting apair on the substrate on which the switching elements and the freewheeling diode elements are mounted, and (b) shows thermal resistancemodels.

[0092] In FIG. 6, reference numeral 15 is the temperature sensor,reference numerals 16 (16 a1, 16 a2, 16 b1, 16 b2, 16 c1, 16 c2, 16 d1,16 d2, 16 e1, 16 e2, 16 f1, 16 f2) are thermal resistances, and Tc (Tc1,Tc2, Tc3, Tc4, Tc5, Tc6) are substrate temperatures.

[0093] Also, Tj_Tr (Tj_Tr1, Tj_Tr2, Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) aretemperatures of the switching elements, and Tj_D (Tj_D1, Tj_D2, Tj_D3,Tj_D4, Tj_D5, Tj_D6) are temperatures of the free wheeling diodeelements. Also, W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6) areheating values (W) of the switching elements calculated based on thesensed currents, and W_D (W_D1, W_D2, W_D3, W_D4, W_D5, W_D6) areheating values (W) of the free wheeling diode elements calculated basedon the sensed currents. Also, r11 is stationary thermal resistances (°C./W) between the switching elements and the substrate, r21 isstationary thermal resistances (° C./W) between the free wheeling diodeelements and the substrate, c11 is transient thermal resistances (°C./W) between the switching elements and the substrate, and c21 istransient thermal resistances (° C./W) between the free wheeling diodeelements and the substrate.

[0094] In the embodiment 1 and the embodiment 2, there is shown theexample in which the temperature sensors are fitted to the switchingelements (Tr1 to Tr6) and the free wheeling diode elements (D1 to D6)and then the temperatures of the switching elements (Tr1 to Tr6) 13 andthe free wheeling diode elements (D1 to D6) 14 are directly sensed.However, in the embodiment 3, the temperature sensors are fitted in thevicinity of the switching elements (Tr1 to Tr6) and the free wheelingdiode elements (D1 to D6) that constitute a pair on the substrate onwhich the switching elements and the free wheeling diode elements aremounted, and then the control portion estimates the temperatures of theswitching elements (Tr1 to Tr6) and the free wheeling diode elements (D1to D6) from the substrate temperature sensed by the temperature sensorsbased on the thermal resistance model.

[0095] In the embodiment 3, the temperatures Tj_Tr (Tj_Tr1, Tj_Tr2,Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) of the switching elements and thetemperatures Tj_D (Tj_D1, Tj_D2, Tj_D3, Tj_D4, Tj_D5, Tj_D6) of the freewheeling diode elements are estimated according to Eq. (13) and Eq. (14)based on the substrate temperatures Tc (Tc1, Tc2, Tc3, Tc4, Tc5, Tc6)sensed by the temperature sensors fitted in the vicinity of theswitching elements and the free wheeling diode elements, which arearranged as pairs, on the substrate on which the switching elements andthe free wheeling diode elements are mounted, the stationary thermalresistances r11, r21, the heating values W_Tr (W_Tr1, W_Tr2, W_Tr3,W_Tr4, W_Tr5, W_Tr6) of the switching elements calculated from thesensed currents, the heating values W_D (W_D1, W_D2, W_D3, W_D4, W_D5,W_D6) of the free wheeling diode elements calculated from the sensedcurrents.

Tj _(—) Tr=Tc+r11×W _(—) Tr   (13)

Tj _(—) D=Tc+r21×W _(—) D   (14)

[0096] For example, the temperature Tj_Tr1 of the switching element Tr1is given by a following equation.

Tj _(—) Tr1=Tc1+r11×W _(—) Tr1

[0097] Also, the temperature Tj_D1 of the free wheeling diode element D1is given by a following equation.

Tj _(—) D1=Tc1+r21×W_D1

[0098] In the embodiment 3, the temperature sensors are fitted in theneighborhood of the switching elements and the free wheeling diodeelements to be a pair on the substrate, and then the temperatures of theswitching elements and the temperatures of the free wheeling diodeelements are estimated based on the thermal resistance models. As aresult, the fitting of the temperature sensors can be facilitated.

[0099] Embodiment 4

[0100]FIG. 7 is a view illustrating temperature measurement of aswitching element and a free wheeling diode element in an inverterdevice according to an embodiment 4 of the present invention, wherein(a) is a view showing an outer appearance of an inverter main circuit inwhich the temperature sensor is fitted to one location of the substrateon which the switching elements and the free wheeling diode elements aremounted, and (b) is thermal resistance models.

[0101] In FIG. 7, reference numeral 15 is the temperature sensor,reference numerals 16 (16 a1, 16 a2, 16 b1, 16 b2, 16 c1, 16 c2, 16 d1,16 d2, 16 e1, 16 e2, 16 f1, 16 f2) are thermal resistances, and Tc isthe substrate temperature sensed by the temperature sensor that isfitted to one location on the substrate on which the switching elementsand the free wheeling diode elements are mounted.

[0102] Also, Tj_Tr (Tj_Tr1, Tj_Tr2, Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) aretemperatures of the switching elements, and Tj_D (Tj_D1, Tj_D2, Tj_D3,Tj_D4, Tj_D5, Tj_D6) are temperatures of the free wheeling diodeelements. Also, W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6) areheating values (W) of the switching elements calculated based on thesensed currents, and W_D (W_D1, W_D2, W_D3, W_D4, W_D5, W_D6) areheating values (W) of the free wheeling diode elements calculated basedon the sensed currents. Also, r11 is the stationary thermal resistances(° C./W) between the switching elements and the substrate, r21 is thestationary thermal resistances (° C./W) between the free wheeling diodeelements and the substrate, c11 is the transient thermal resistances (°C./W) between the switching elements and the substrate, and c21 is thetransient thermal resistances (° C./W) between the free wheeling diodeelements and the substrate.

[0103] In the embodiment 3, there is shown the example in which thetemperature sensors are fitted in vicinity of the switching elements andthe free wheeling diode elements constituting a pair on the substrate onwhich the switching elements and the free wheeling diode elements aremounted. In the embodiment 4, the temperature sensor is fitted to onelocation on the substrate on which the switching elements and the freewheeling diode elements are mounted.

[0104] In the embodiment 4, the temperatures Tj_Tr (Tj_Tr1, Tj_Tr2,Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) of the switching elements and thetemperatures Tj_D (Tj_D1, Tj_D2, Tj_D3, Tj_D4, Tj_D5, Tj_D6) of the freewheeling diode elements are estimated according to Eq. (13) and Eq. (14)based on the substrate temperature Tc sensed by the temperature sensorsfitted to one location on the substrate on which the switching elementsand the free wheeling diode elements are mounted, the stationary thermalresistances r11, r21, the heating values W_Tr (W_Tr1, W_Tr2, W_Tr3,W_Tr4, W_Tr5, W_Tr6) of the switching elements calculated based on thesensed currents, and the heating values W_D (W_D1, W_D2, W_D3, W_D4,W_D5, W_D6) of the free wheeling diode elements calculated based on thesensed currents as with like the embodiment 3.

Tj _(—) Tr=Tc+r11×W _(—) Tr   (13)

Tj _(—) D=Tc+r21×W _(—) D   (14)

[0105] For example, the temperature Tj_Tr1 of the switching element Tr1is given by a following equation.

Tj _(—) Tr1=Tc+r11×W _(—) Tr1

[0106] Also, the temperature Tj_D1 of the free wheeling diode element D1is given by a following equation.

Tj _(—) D1=Tc+r21×W _(—) D1

[0107] In the embodiment 4, the temperature sensor is fitted to onelocation of the substrate on which the switching elements and the freewheeling diode elements are mounted, and then the temperatures of theswitching elements and the temperatures of the free wheeling diodeelements are estimated based on the thermal resistance models. As aresult, the fitting of the temperature sensor can be made much moreeasy.

[0108] Embodiment 5

[0109]FIG. 8 is a view illustrating the temperature measurement of theswitching element and the free wheeling diode element in an inverterdevice according to an embodiment 5 of the present invention, wherein(a) is a view showing an outer appearance of an inverter main circuit,(b) is a view showing a sectional shape of the inverter main circuit inwhich the temperature sensors are fitted to portions of a cooling fincorresponding to the switching elements and the free wheeling diodeelements, respectively, and (c) is thermal resistance models. Here, FIG.8(b) shows an example in which the temperature sensors are fitted to thecooling fin under the switching elements (Tr1, Tr2) and the freewheeling diode elements (D1, D2).

[0110] In FIG. 8, reference numeral 10 is the cooling fin, referencenumeral 11 is the main circuit substrate, reference numeral 12 is thecase, reference numeral 15 is the temperature sensor, Tr1 to Tr6 are theswitching elements, and D1 to D6 are the free wheeling diode elements.

[0111] Also, Tf_Tr (Tf_Tr1, Tf_Tr2, Tf_Tr3, Tf_Tr4, Tf_Tr5, Tf_Tr6) arefin temperatures corresponding to the switching elements sensed by thetemperature sensors, Tf_D (Tf_D1, Tf_D2, Tf_D3, Tf_D4, Tf_D5, Tf_D6) arefin temperatures corresponding to the free wheeling diode elementssensed by the temperature sensors, Tc_Tr (Tc_Tr1, Tc_Tr2, Tc_Tr3,Tc_Tr4, Tc_Tr5, Tc_Tr6) are substrate temperatures corresponding to theswitching elements, and Tc_D (Tc_D1, Tc_D2, Tc_D3, Tc_D4, Tc_D5, Tc_D6)are substrate temperatures corresponding to the free wheeling diodeelements.

[0112] Also, Tj_Tr (Tj_Tr1, Tj_Tr2, Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) arethe temperatures of the switching elements, and Tj_D (Tj_D1, Tj_D2,Tj_D3, Tj_D4, Tj_D5, Tj_D6) are the temperatures of the free wheelingdiode elements. Also, W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6)are heating values (W) of the switching elements calculated based on thesensed currents, and W_D (W_D1, W_D2, W_D3, W_D4, W_D5, W_D6) areheating values (W) of the free wheeling diode elements calculated basedon the sensed currents. Also, r11 is the stationary thermal resistances(° C./W) between the switching elements and the substrate, r21 is thestationary thermal resistances (° C./W) between the free wheeling diodeelements and the substrate, r12 is a stationary thermal resistance (°C./W) between the fin and the substrate, and r22 is a stationary thermalresistance (° C./W) between the fin and the substrate. Also, c11 is thetransient thermal resistances (° C./W) between the switching elementsand the substrate, c21 is the transient thermal resistances (° C./W)between the free wheeling diode elements and the substrate, c12 is atransient thermal resistance (° C./W) between the fin and the substrate,and c22 is a transient thermal resistance (° C./W) between the fin andthe substrate.

[0113] In the embodiment 5, the temperatures Tj_Tr (Tj_Tr1, Tj_Tr2,Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) of the switching elements and thetemperatures Tj_D (Tj_D1, Tj_D2, Tj_D3, Tj_D4, Tj_D5, Tj_D6) of the freewheeling diode elements are estimated according to Eq. (15) and Eq. (16)based on the fin temperatures Tf_Tr (Tf_Tr1, Tf_Tr2, Tf_Tr3, Tf_Tr4,Tf_Tr5, Tf_Tr6) corresponding to the switching elements sensed by thetemperature sensors, the fin temperatures Tf_D (Tf_D1, Tf_D2, Tf_D3,Tf_D4, Tf_D5, Tf_D6) corresponding to the free wheeling diode elementssensed by the temperature sensors, the stationary thermal resistancesr11, r21, the heating values W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5,W_Tr6) of the switching elements calculated based on the sensedcurrents, and the heating values W_D (W_D1, W_D2, W_D3, W_D4, W_D5,W_D6) of the free wheeling diode elements calculated based on the sensedcurrents.

Tj _(—) Tr=Tf _(—) Tr+(r11+r12)×W _(—) Tr   (15)

Tj _(—) D=Tf _(—) D+(r21+r22)×W _(—) D   (16)

[0114] For example, the temperature Tj_Tr1 of the switching element Tr1is given by a following equation.

Tj _(—) Tr1=Tf _(—) Tr1+(r11+r12)×W _(—) Tr1

[0115] Also, the temperature Tj_D1 of the free wheeling diode element D1is given by a following equation.

Tj _(—) D1=Tf _(—) D1+(r21+r22)×W _(—) D1

[0116] In the embodiment 5, the temperature sensors are fitted to thecooling fin at the locations corresponding to the switching elements andthe free wheeling diode elements respectively, and then the temperaturesof the switching elements and the temperatures of the free wheelingdiode elements are estimated based on the thermal resistance models. Asa result, the fitting of the temperature sensors can be furtherfacilitated.

[0117] Embodiment 6

[0118]FIG. 9 is a view illustrating the temperature measurement of theswitching element and the free wheeling diode element in an inverterdevice according to an embodiment 6 of the present invention, wherein(a) is a view showing an outer appearance of the inverter main circuit,(b) is a view showing a sectional shape of the inverter main circuit inwhich the temperature sensors are fitted to the cooling fin tocorrespond to the switching elements and the free wheeling diodeelements that constitute pairs, and (c) is the thermal resistancemodels. FIG. 9(b) shows an example in which the temperature sensors arefitted to the cooling fin under the switching element Tr1 and the freewheeling diode element D1 constituting a pair, and under the switchingelement Tr2 and the free wheeling diode element D2 constituting a pair.

[0119] In FIG. 9, reference numeral 10 is the cooling fin, referencenumeral 11 is the main circuit substrate, reference numeral 12 is thecase, reference numeral 15 is the temperature sensor, Tr1 to Tr6 are theswitching elements, and D1 to D6 are the free wheeling diode elements.

[0120] Also, Tf (Tf1, Tf2, Tf3, Tf4, Tf5, Tf6) are the fin temperaturessensed by the temperature sensors, Tc_Tr (Tc_Tr1, Tc_Tr2, Tc_Tr3,Tc_Tr4, Tc_Tr5, Tc_Tr6) are the substrate temperatures corresponding tothe switching elements, and Tc_D (Tc_D1, Tc_D2, Tc_D3, Tc_D4, Tc_D5,Tc_D6) are the substrate temperatures corresponding to the free wheelingdiode elements.

[0121] Also, Tj_Tr (Tj_Tr1, Tj_Tr2, Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) arethe temperatures of the switching elements, and Tj_D (Tj_D1, Tj_D2,Tj_D3, Tj_D4, Tj_D5, Tj_D6) are the temperatures of the free wheelingdiode elements. Also, W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6)are the heating values (W) of the switching elements calculated based onthe sensed currents, and W_D (W_D1, W_D2, W_D3, W_D4, W_D5, W_D6) arethe heating values (W) of the free wheeling diode elements calculatedbased on the sensed currents. Also, r11 is the stationary thermalresistances (° C./W) between the switching elements and the substrate,r21 is the stationary thermal resistances (° C./W) between the freewheeling diode elements and the substrate, r12 is the stationary thermalresistance (° C./W) between the fin and the substrate, and r22 is thestationary thermal resistance (° C./W) between the fin and thesubstrate. Also, c11 is the transient thermal resistances (° C./W)between the switching elements and the substrate, c21 is the transientthermal resistances (° C./W) between the free wheeling diode elementsand the substrate, c12 is the transient thermal resistance (° C./W)between the fin and the substrate, and c22 is the transient thermalresistance (° C./W) between the fin-the substrate.

[0122] In the embodiment 5, there is shown the example in which thetemperature sensors are fitted to the cooling fin to correspond to theswitching elements and the free wheeling diode elements respectively.However, in the embodiment 6, the temperature sensors are fitted to thecooling fin to correspond to the switching elements and the freewheeling diode elements that constitute pairs.

[0123] In the embodiment 6, the temperatures Tj_Tr (Tj_Tr1, Tj_Tr2,Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) of the switching elements and thetemperatures Tj_D (Tj_D1, Tj_D2, Tj_D3, Tj_D4, Tj_D5, Tj_D6) of the freewheeling diode elements are estimated according to Eq. (17) and Eq. (18)based on the fin temperatures Tf (Tf1, Tf2, Tf3, Tf4, Tf5, Tf6) sensedby the temperature sensors, the stationary thermal resistances r11, r12,r21, r22, the heating values W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5,W_Tr6) of the switching elements calculated based on the sensedcurrents, and the heating values W_D (W_D1, W_D2, W_D3, W_D4, W_D5,W_D6) of the free wheeling diode elements calculated based on the sensedcurrents.

Tj _(—) Tr=Tf+(r11+r12)×W _(—) Tr   (17)

Tj _(—) D=Tf+(r21+r22)×W _(—) D   (18)

[0124] For example, the temperature Tj_Tr1 of the switching element Tr1is given by a following equation.

Tj _(—) Tr1=Tf+(r11+r12)×W _(—) Tr1

[0125] Also, the temperature Tj_D1 of the free wheeling diode element D1is given by a following equation.

Tj _(—) D1=Tf+(r21+r22)×W _(—) D1

[0126] In the embodiment 6, the temperature sensors are fitted to thecooling fin so as to correspond to the switching elements and the freewheeling diode elements constituting pairs, and then the temperatures ofthe switching elements and the temperatures of the free wheeling diodeelements are estimated based on the thermal resistance models. As aresult, the fitting of the temperature sensors can be much morefacilitated.

[0127] Embodiment 7

[0128]FIG. 10 is a view illustrating the temperature measurement of theswitching element and the free wheeling diode element in an inverterdevice according to an embodiment 7 of the present invention, wherein(a) is a view showing an outer appearance of the inverter main circuit,(b) is a view showing a sectional shape of the inverter main circuit inwhich the temperature sensor is fitted to one location of the coolingfin, and (c) is the thermal resistance models.

[0129] In FIG. 10, reference numeral 10 is the cooling fin, referencenumeral 11 is the main circuit substrate, reference numeral 12 is thecase, 15 is the temperature sensor, Tr1 to Tr6 are the switchingelements, and D1 to D6 are the free wheeling diode elements.

[0130] Also, Tf is the fin temperature sensed by the temperature sensor,Tc_Tr (Tc_Tr1, Tc_Tr2, Tc_Tr3, Tc_Tr4, Tc_Tr5, Tc_Tr6) are the substratetemperatures corresponding to the switching elements, and Tc_D (Tc_D1,Tc_D2, Tc_D3, Tc_D4, Tc_D5, Tc_D6) are the substrate temperaturescorresponding to the free wheeling diode elements.

[0131] Also, Tj_Tr (Tj_Tr1, Tj_Tr2, Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) arethe temperatures of the switching elements, and Tj_D (Tj_D1, Tj_D2,Tj_D3, Tj_D4, Tj_D5, Tj_D6) are the temperatures of the free wheelingdiode elements. Also, W_Tr (W_Tr1, W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6)are the heating values (W) of the switching elements calculated based onthe sensed current, and W_D (W_D1, W_D2, W_D3, W_D4, W_D5, W_D6) are theheating values (W) of the free wheeling diode elements calculated basedon the sensed current. Also, r11 is the stationary thermal resistances(° C./W) between the switching elements and the substrate, r21 is thestationary thermal resistances (° C./W) between the free wheeling diodeelements and the substrate, r12 is the stationary thermal resistance (°C./W) between the fin and the substrate, and r22 is the stationarythermal resistance (° C./W) between the fin and the substrate. Also, c11is the transient thermal resistances (° C./W) between the switchingelements and the substrate, c21 is the transient thermal resistances (°C./W) between the free wheeling diode elements and the substrate, c12 isthe transient thermal resistance (° C./W) between the fin and thesubstrate, and c22 is the transient thermal resistance (° C./W) betweenthe fin and the substrate.

[0132] In the embodiment 6, there is shown the example in which thetemperature sensors are fitted to the cooling fin to correspond to theswitching elements and the free wheeling diode elements, whichconstitute pairs. However, in the embodiment 7, the temperature sensoris fitted to one location of the cooling fin.

[0133] In the embodiment 7, the temperatures Tj_Tr (Tj_Tr1, Tj_Tr2,Tj_Tr3, Tj_Tr4, Tj_Tr5, Tj_Tr6) of the switching elements and thetemperatures Tj_D (Tj_D1, Tj_D2, Tj_D3, Tj_D4, Tj_D5, Tj_D6) of the freewheeling diode elements are estimated according to Eq. (19) and Eq. (20)based on the fin temperatures Tf sensed by the temperature sensor, thestationary thermal resistances r11, r12, the heating values W_Tr (W_Tr1,W_Tr2, W_Tr3, W_Tr4, W_Tr5, W_Tr6) of the switching elements calculatedbased on the sensed current, and the heating values W_D (W_D1, W_D2,W_D3, W_D4, W_D5, W_D6) of the free wheeling diode elements calculatedbased on the sensed current.

Tj _(—) Tr=Tf+(r11+r12)×W _(—) Tr   (19)

Tj _(—) D=Tf+(r21+r22)×W _(—) D   (20)

[0134] For example, the temperature Tj_Tr1 of the switching element Tr1is given by a following equation.

Tj _(—) Tr1=Tf+(r11+r12)×W _(—) Tr1

[0135] Also, the temperature Tj_D1 of the free wheeling diode element D1is given by a following equation.

Tj _(—) D1Tf+(r21+r22)×W_(—) D1

[0136] In the embodiment 7, the temperature sensor is fitted to onelocation of the cooling fin, and then the temperatures of the switchingelements and the temperatures of the free wheeling diode elements areestimated based on the thermal resistance models. As a result, thefitting of the temperature sensors becomes easy much more.

[0137] Industrial Applicability

[0138] As described above, the power converter device according to thepresent invention can estimate the saturation voltages of respectiveswitching elements and execute the power conversion to output thecommand voltage with good precision. Therefore, the power converterdevice is suitable for the applications such as the conveyer, thecarriage, etc. in which such power converter device is employed in thelow-speed operation range.

1. A power converter device comprising: an inverter portion having aswitching element and a free wheeling diode element, the inverterportion for converting a DC power into an AC power; a control portionfor ON/OFF-controlling the switching elements of the inverter portion;and a current sensor for sensing current flowing through one of theswitching element and the free wheeling diode element, wherein thecontrol portion comprises: a current discriminating circuit fordiscriminating that sensed currents sensed by the current sensors areeither current flowing through the switching elements or current flowingthrough the free wheeling diode elements; a saturation voltageestimation table for showing relationships between temperature of theswitching element, current value of the switching element, temperatureof the free wheeling element, and current value of the free wheelingelement and saturation voltages of the switching elements; and asaturation voltage compensating unit for receiving the temperature ofthe switching element and the current discriminated by the currentdiscriminating circuit, estimating a saturation voltage of the switchingelement by using the saturation voltage estimation table, and formingsaturation voltage compensated voltage in which a command voltage to aninverter is compensated with the estimated saturation voltage, andwherein the switching elements of the inverter portion areON/OFF-controlled based on the saturation voltage compensated voltage.2. A power converter device comprising: an inverter portion having aswitching element and a free wheeling diode element, the inverterportion for converting a DC power into an AC power; a control portionfor ON/OFF-controlling the switching elements of the inverter portion;and a gate voltage detecting circuit insulating circuit for detectinggate voltage of the switching element, wherein the control portioncomprises: a current discriminating circuit for discriminating thatsensed currents sensed by the current sensors are either current flowingthrough the switching elements or current flowing through the freewheeling diode elements; a saturation voltage estimation table forshowing relationships between temperature of the switching element,current value of the switching element, temperature of the free wheelingelement, and current value of the free wheeling element and saturationvoltages of the switching elements; and a saturation voltagecompensating unit for receiving the gate voltage of the switchingelement and the current discriminated by the current discriminatingcircuit, estimating a saturation voltage of the switching element byusing the saturation voltage estimation table, and forming saturationvoltage compensated voltage in which a command voltage to an inverter iscompensated with the estimated saturation voltage, and wherein theswitching elements of the inverter portion are ON/OFF-controlled basedon the saturation voltage compensated voltage.
 3. The power converterdevice according to any one of claims 1 and 2, wherein temperaturesensors are fitted to the switching element and the free wheeling diodeelement to sense temperature of the switching element and temperature ofthe free wheeling diode element.
 4. The power converter device accordingto any one of claims 1 and 2, wherein temperature sensor is fitted inthe vicinity of the switching element and the free wheeling diodeelement, which constitute a pair, on a substrate on which the switchingelement and the free wheeling diode element are mounted; and wherein thecontrol portion estimates temperature of the switching element andtemperature of the free wheeling diode element based on substratetemperature sensed by the temperature sensor, stationary thermalresistance between the switching element and the substrate, stationarythermal resistances between the free wheeling diode element and thesubstrate, heating value of the switching element calculated based onthe sensed current, and heating value of the free wheeling diode elementcalculated based on the sensed current.
 5. The power converter deviceaccording to any one of claims 1 and 2, wherein a temperature sensor isfitted to one location on a substrate on which the switching element andthe free wheeling diode element are mounted; and wherein the controlportion estimates temperature of the switching element and temperatureof the free wheeling diode element based on substrate temperature sensedby the temperature sensor, stationary thermal resistance between theswitching element and the substrate, stationary thermal resistancesbetween the free wheeling diode element and the substrate, heating valueof the switching element calculated based on the sensed current, andheating value of the free wheeling diode element calculated based on thesensed current.
 6. The power converter device according to any one ofclaims 1 and 2, wherein temperature sensors are fitted to a location ona fin fitted to a substrate on which the switching element and the freewheeling diode element are mounted, the location corresponding to theswitching element and the free wheeling diode element; and wherein thecontrol portion estimates temperature of the switching element and thefree wheeling diode element based on substrate temperature sensed by thetemperature sensors, stationary thermal resistance between the switchingelement and the substrate, stationary thermal resistance between the finand the substrate, stationary thermal resistance between the freewheeling diode element and the substrate, the stationary thermalresistance between the fin-the substrate and heating values of theswitching element calculated based on the sensed currents, and heatingvalues of the free wheeling diode element.
 7. The power converter deviceaccording to any one of claims 1 and 2, wherein temperature sensor arefitted to a location on a fin fitted to a substrate on which theswitching element and the free wheeling diode element are mounted, thelocation corresponding to a pair of the switching element and the freewheeling diode element; and wherein the control portion estimatestemperature of the switching element and temperature of the freewheeling diode element based on substrate temperature sensed by thetemperature sensor, stationary thermal resistances between the switchingelement and the substrate, a stationary thermal resistance between thefin and the substrate, stationary thermal resistances between the freewheeling diode element and the substrate, the stationary thermalresistance between the fin and the substrate, heating value of theswitching element calculated based on the sensed current, and heatingvalue of the free wheeling diode element calculated based on the sensedcurrent.
 8. The power converter device according to any one of claims 1and 2, wherein temperature sensor is fitted to one location on a finthat is fitted to a substrate on which the switching element and thefree wheeling diode element are mounted; and wherein the control portionestimates temperature of the switching element and temperature of thefree wheeling diode element based on substrate temperature sensed by thetemperature, stationary thermal resistances between the switchingelement and the substrate, stationary thermal resistance between the finand the substrate, stationary thermal resistances between the freewheeling diode element and the substrate, stationary thermal resistancebetween the fin and the substrate, heating value of the switchingelement calculated based on the sensed current, and heating value of thefree wheeling diode element based on the sensed current.